One problem related to transmission stuck in gear has been reported for the 1999 Hyundai Elantra. The most recently reported issues are listed below.
I bought the car brand new. After about 8 months the car would get stuck in second gear when slow down. The car also kicks very hard while it does this. One time I was rounding a turn after it rained and as I slowed down around the corner the car kicked and the rear end of the car slid out into the plastic divider poles between the lanes. The poles caused a ding in the car an cracked a window. At the time it happened so fast I thought I had hit something and only a week later when the car kicked again did I realize that was probably what happened. I brought the car down to the dealer and was told I would be given a new pulse generator under warranty. Then there was a recall on a part in the transmission and that was fixed. The problem still persisted and I have had the pulse generator changed four more times. My warranty is now up and the problem has come back. I have even installed a brand knew transmission.